Adaptively Steered Antenna Array and Receiver Testing with Multi-RF Output GNSS Simulator NavXR -NCS Professional

Abstract

The NavX-NCS Professional GNSS Simulator may be fitted with up to 4 independent RF outputs. Potentially multiple RF outputs could be used to simulate multiple vehicles (for example, for real time kinematic (RTK) or formation flying scenarios), or multiple antennas on the same vehicle (for example, for attitude determination scenarios), or for separate elements of a Controlled Reception Pattern Antenna (CRPA). In addition to the independent RF outputs the Simulator would also be fitted with a combined RF output for standard single output testing. Tests are performed with the GALANT multi-antenna GNSS receiver developed by DLR. GALANT utilities an array antenna with four radiator elements and applies adaptive array processing after correlation of the signals of each of the four antenna channels. Because the array processing is applied after correlation, the directions of arrival of the GNSS satellite can be estimated and individual antenna beams can be adaptively steered to the satellites in view by adaptive digital beam forming. Additionally, strong interference signals are suppressed by generation of nulls during the beam forming process. By comparison of the estimated satellite directions with the known satellite positions from the decoded almanac the attitude of the array itself can be determined. In order to achieve a high accuracy in the direction of arrival estimations and the attitude determination a continuous calibration of the differential carrier phases between the four receiver hardware channels is performed by utilization of a special PRN code. The achieved accuracy is about 1°. For real antenna measurements the calibration PRN code is generated internally within the receiver, mixed up to RF and fed into four calibration inputs of the array antenna. However, in the hardware simulations no antenna is used and the simulator signals are directly fed into the receiver RF frontend. Therefore, the calibration code is generated by the NavX-NCS simulator. Exemplary results of different static and dynamic test scenarios will be presented